Production of 1, 4-dichlorobutane



United States Patent 2,889,380 PRODUCTION OF 1,4-DICHLOROBUTANE' EdwardE. Hamel, Niagara Falls, N.Y., assignor to E. I. du Pont de N emours andCompany, Wilmington, Del., a corporation of Delaware No Drawing.Application October 15,1956

Serial N0. 615,766 9 7 6 Claims. or. 260-657) This application, acontinuation-in-part of my co-pend ing application, Serial No. 393,500,filed November 20, 1953, now abandoned, relates to the dichlorobutanefrom tetrahydrofuran.

production of 1,4-

2,889,380 Patented June 2, 1959 new and improved method for producing1,4-dichlorobutane by the liquid phase reaction of tetrahydrofuran1,4-dichlorobutane from tetrahydrofuran and hydrogen chloride that willminimize formation of by-product 4,4?- dichlorodibutyl ether. A stillfurther object is provision of a' continuous process for the'productionof 1,4 di- 1,4-dichlorobutane is valuable as an intermediate in the Iproduction of nylon. An important commercial source of the material isfrom the reaction of hydrogen chloride with tetrahydrofuran:

( H2COH] Tetrahydrofuran lA-dlchlorobutane This reaction also yields4,4-dichlorodibutyl.ether as a chlorobutane from hydrogen chloride andtetrahydrofuran by the aforesaid liquid phase reaction. An additionalobject is a method for producing 1,4-dichlorobutane which avoids theneed for expensive catalysts and can be operated at a commerciallyacceptable pressure.

The above-mentioned and still further objects of the invention areachieved by an essentially non-catalytic process in whichtetrahydrofuran is heated with an excess over the stoichiometricalamount of hydrogen chlo rride in the form of an aqueous solutioncontaining not by-product so that the crude 1,4-dichlorobutanemay con-.1

tain up to 10% by weight or more of this material. The formation of thisby-product is indicated by the equation:

H; OH; 2HC1=CI(CH2)40(CH2)AC1 H 0 Trieschmann et al., German Patent859,734 Decem ber 15, 1952) employ anhydrous reagents alone and in thepresence of a metal chloride catalyst such as bismuth chloride.Codignola et al., French Patent 1,045,827 (July 1, 1953) carry out acontinuous gas-phase reaction with anhydrous reagents. Cass,'U.S. Patent2,218,018

r. the success of the process is dependent upon the separa- (Oct. 15,1940) uses a 'dehydrating'ag ent such as sulfuric acid. Scott, US.Patent 2,491,834 (December 20, 1949) employs quaternary ammonium halidecatalysts "and Kroper, German Patent 859,884 (February 5,, 1953) employsaqueous hydrogen chloride with bismuth 'eihlo'ride" or sulfuric acid. q,I I i In general, processes employing catalysts and dehydrat-' ingagents are disadvantageous in that the catalysts are expensive. Also,product recovery problems are complicated by the use of both dehydratingagents and catalysts. Furthermore, all of these processes tend to giverelatively high yields of theby-product, 4,4'-dichlorodibutyl ether sothat the crude 1,4-dichlorobutane may contain over 4% by weight of thisimpurity.

over 45% hydrogen chloride by weight at an autogenous pressure in therange of 50 to 150 lbs. p.s.i.g. (pounds per square inch gauge).Temperatures in the range 140 to 150 C. and pressures under 100 p.s.i.g.are preferred.

- Best results are obtained when the aqueous acid contains at leastthree moles hydrogen chloride per mole of tetrahydrofuran. The moleratio of hydrogen chloride to tetrahydrofuran and the concentration ofhydrogen chloride and water in the reaction mixture are critical sincetion of product as a non-aqueous upper phase which can be readilydecanted from the reaction mixture. These factors must be adjusted sothat the concentration of hydrogen chloride in the aqueous phase of thereaction mixture does not fall below 20% by weight. For optimum resultsthis concentration should be in the range 25 to 35% by weight. Under thepreferred conditions, the nonaqueous product phase contains1,4-dichlorobutane as a major constitutent in approximately 95% yield.The 4,4- dichlorodibutyl ether formed under these circumstances equals 1to 3% by weight of the crude 1,4-dichlorobutane. The reaction is rapidand requires onlyabout 10 to 30 minutes for completion.

A continuous process may be used to advantage if so desired. This isreadily accomplished by feeding tetrahydrofuran and hydrogen chloridegas in a mole ratio of about 1:2 into the bottom of a reactor containinga large excess of hot aqueous 25 to 35% hydrogen chloride underautogeneous pressure at a temperature of 140 to 150 C. and decanting orflowing out the non-aqueous organic phase from the top of the reactor asformed together with aqueous phase containing one molecular proportionof water for each mole of 1,4-dichlorobutane which is the majorconstituent of the organic phase. This is readily accomplished bypositioning an over-flow pipe The use of anhydrous raw materials, anddehydrating agents in prior art processes is based on the premise that.

optimum yields are obtainablefrom a reaction yielding water when themass action efiect of the wateris minimized by reducing itsconcentration in the reaction mix-.

ture. It has now been found that high yields of llflgdi chlorobutane canbeobtained in a process employingv aqueous hydrogen chloride in thealysts.

absence of added catpresent avenue is; rovision a: a

at the level to which the reactor is initially filled with hot aqueoushydrogen chloride. The over-flow will then be equivalent to the combinedvolume of the aqueous and non-aqueous product formed by the reaction.phases can then be subjected to distillation and 'decantation toseparate unreacted tetrahydrofuran, 4,4'-dichlorodibutyl ether andaqueous hydrogen chloride from the 1,4-dichlorobutane produced. Ifdesired, the tetrahydrofuran and the 4,4'-dichlorodibutyl ether can berecycled .tothe reactor. In carrying out this process, the hydrogenchloride feed should be adjusted to maintain the hydrogen chloridecontent of the aqueous product phase in the 25 to 35% range.

Numerous variations can be made inthis process withg in the scope of theinvention. Temperatures ranging from I These O l20-to 170 C. may beemployed. The concentration of hydrogen chloride in the aqueous phase ofthe reaction mixture may range from about 20% hydrogen chloride to 45%.However, since pressures in excess of 150 p.s.i.g;

hydrofuran may be added to l20 or even greater molar proportions-ofhydrogen chloride, the hydrogen chloridetetrahydrofuran-ratio beinglimited only by the rate of reaction or hold-up in a given reactor.

The by-products of the tetrahydrofuran-hydrogen chlo-- ride' reactioninclude the intermediate tetramethylene chlorhydrirr in addition to4,4'-dichlorodibutyl ether.

Tetramethylene chlorhydrin is a product of the equilibri urn reaction:

Tetrahydrofuran Tetramethylene chlorhydrin Reaction withadditional-hydrogen chloride converts this product to1,4-dichlorobutane; autocondensation gives 4,4-dichlorodibutylether.Because of its solubility in aqueous hydrogen chloride, tetramethylenechlorhydrintends to'accumulate in the aqueous phase and is kept'to aminimum by employing excess hydrogen chloride. A

low hydrogen chloride-tetrahydrofuran ratio may yielda single phasereactionrnixturedepending on the water content-since tetramethylenechlorhydrinalso increases the'solubility of 1,4-dichlorobutane in theaqueous phase.

While some 4,4-dichl'orodibutyl ether is invariably formed by theprocess of this invention, the amount formed is kept to a minimum-by theconditions employed. Temperature is an important factor. A batchpreparation employing thepreferred reagent proportions at 110* C. yieldsa crude dichlorobutane containing 25% dichlorodibutyl ether whereas theconcentration of this byproduct is about 2% when the reaction is carriedout at 150 C.

Although only small amounts of by-product 4,4'-dichlorodibutyl ether andtetramethylene chlorhydn'n are produced by the process-of thisinventiomyield losses due to their formationcanbe avoided by recoveryprocesses. On'distillation, tetramethylene chlorhydrin in the aque oushydrogen chloride phase is converted to tetrahydrofuran whichcan berecycled to the pressure reactor. 4,4- dichlorodibutyl ether ishydrolyzed by hot aqueous hydrogen chloride to yield tetramethylenechlorhydrin which then reacts to give 1,4-dichlorobutane. Build-upoftheether in the reactor apparently reaches an equilibrium-- or steady statewhen its concentration in the feed reaches 2-3.4 weight percent.Consequently the material can be reworked if necessary by batch orcontinuous process. It is readily separated from 1,4-dichlorobutane byfrac'-' tional distillation.

The preferred recovery technique of this process inpr'oduct phases toremove tetrahydrofuran. The. tetrahydrofuran obtained in this Wayincludes unreacted tetra- Some 4,4' -dichlorodibutyl ether isalsohydrolyzed during the tetrahydrofuran stripping yielding additionaltetramethylene chlorhydrin which also contributes to the tetrahydrofuranrecovery. Stripped non-aqueous product is then neutralized by Washingwith an aqueous alkali to remove hydrogen chloride, after which thel,4-dichlorobutaneis, distilled leavinga still residue containing anyunreacted '4,4"-dichlorodibutyl ether.

As previonsly-pointed out, separation of the 1,4-dichlorobutane from thereaction ofitetrahydrofuran and aqueous hydrochloric acid asan upper,non-aqueous organic phase is a critical feature of this invention.Experiments have demonstrated that the desiredseparation will take placeif the concentration of hydrogen chloride in the aqueous phase'ofi'thereaction mixture is not less than about a -35% concentration beingpreferred for optimum yields. Separation of product as a lower phase-will -take place if the hydrogen chloride convolves distillation of themixed aqueous and non-aqueous? hydrofuran andftetrahydr'ofuran producedby the splitting of hydrogen chloride from tetramethylene chlorhyd'n'n.

cent-ration is allowed -to reachlower values but yieldsandreaetion-rates are unfavorable under conditions that would result inthis situation. In-this connection it should be -pointed out thatthe-factors determiningthe desired phase separationare-extremelyicomplex; The density of the aqueousand non aqueous phasesis dependent on: their composition and the components involvedincludetetramethylene chlorhydrin, tetrahydrofuran and dichloro-,dibutyl ether as well as hydrogen chloride, dichlorobutane and water.Distribution factors aud'the difierential efiect of temperature vondensity are also involved. Data on phase separation of product mixturesin Table I shows thatthecritical hydrogen chloride concentration isabout 20%":byj weight: In'this table, 'tetramethylene chlorhydrin isdesignatedlas- TMC.

TABLE I.PHASE SEPARATION IN DIGI-ILORO- BUTANE PROCESS Position oforganic Gone. in an. layer at Separaphase Exp. tion of a p layers C.Room H01 TMC Temp.

Example I This example shows results obtainable in batchpreparationswhen the compo'sition'of the reaction mixture is neanoptimumand temperatures are varied.

Aiseries of runs was carried out in separate sealed glass"tubes atvarioustemperatures under autogenous pressure; The temperaturewas'maintained by inserting thet'ubeslin athermostated liquidlbath; Thetubes were agitated-by shaking duringthe time allowed for reaction.since the reaction rate decreases withtemperature, longer heatingperiods were allowed for the lowerv temperatures.

The composition of thereaction mixture in weight percent is indicatedbelow together with the mole ratio of the, reagents:

Weight Mole percent ratlo Tetrahydrofuran 12. 47 1 Hydrogen Chlorlde33.91 5 Water 53. 62 17. 2

:The above can be obtained by mixing 38.8% aqueous hydrogen chloridewith tetrahydrofuran. It should be noted that this mixture contains 17.2times the amount of water that would be formed by quantitativeproduction of 1,4-dich1orobutane.

TABLE II.REACTIONS IN THF:HCl:H2O MIXTURE OF MOLE RATIO 1:5:l7.2

Tempcra- Maximum Contact 1 Mole Per- Product Run ture (/C.) pressure imecent THF DCBzDDE (p.s.i.g.) (minutes) conversion ratio 1 This is thereaction time or the length of time the reactants were in contact andagitation was maintained.

These data show that the optimum reaction temperature is around 150 C.with a concomitant autogenous pressure of around 90 p.s.i.g. It shouldbe noted that the yield of 1,4-dichlor0-butane falls ofi as thetemperature is'decreased and that the yield of by-product etherincreases even though alonger contact time was allowed at120; C. Thegiven contact time includes a short heating period and is consequentlysomewhat longer than the actual reaction time.

The final concentration of aqueous hydrogen chloride in the experimentsat 150 C. was approximately 26%. These results indicate that reactiontemperatures below 120 C. would be too low for practical purposes.

Example II TABLE III.REACTIONS IN THFzHclzHgO MIXTURE OF MOLE RATIO12414.39

Tempera- Contact Mole Per- Product Run ture (/C.) time cent THF DCBzDDE(minutes) conversion ratio It will be seen that reducing the mole ratioof hydrogen chloride to tetrahydrofuran from 5:1 to 4:1, not onlydecreases the yield of 1,4-dich1orobutane but also increases 6 the yieldof by-product ether. The initial concentration of aqueous hydrogenchloride in this batch experiment was 36.1%. The final concentration ofthe aqueous hydrogen chloride phase in the experiment at 150 C. wasapproximately 23%.

Example 111 The procedure of Examples 1 and 2 was substantially repeatedwith a mixture having TI-IF:HC1:H O mole ratio of 1.00:3.00:10.81.Conversions in a 64 minute contact time at 140 C. and 150 C. were 58.8and 77.6

mole percent 1,4-dichlorobutane respectively. The cor responding DCBzDDEweight ratios in the final products were 2.69 and 11.36 respectively. Inthese runs, the initial concentration of the aqueous hydrogen chloridewas 36.1%. However, in the 140 C. run the lower aqueous phase had aconcentration of approximately 22% whereas in the 150 C. run the aqueousphase was the upper phase and the hydrogen chloride concentratiien inthis phase was about 16%.

Example IV The procedure of the previous runs was repeated with areaction mixture having a THFzHclzH O mole ratio of 1:1:3.6. Conversionsin 64 minutes contact time were 16.7 mole percent 1,4-dichlorobutane at140 C. and 21.1 mole percent at 150 C. The respective DCBzDDE weightratios were 1.54 and 1.80 respectively. In this experiment, thetetrahydrofuran was in excess and although the aqueous hydrogen chloridehad an initial concentration of 36.1%, results were completelyunsatisfiactory "in that the yields of 1,4-dichlorobutane were low andthe crude product contained between 35 and 40% by weight of4,4'-dichlorodibutyl ether.

Example V This example illustrates an embodiment of the invention in acontinuous process as carried out in plant scale equipment.

A glass-lined, cylindrical, steel pressure reactor was charged withapproximately 10,000 pts. by weight of aqueous hydrogen chloridecontaining 26 to 28% hydrogen chloride by weight. This reactor wasequipped with bottom inlets for feeding raw materials and a liquidproduct over-flow pipe slightly above initial level of the acid charge.It was also equipped with an outlet pipe situated at the top of thereactor for venting air and other gases. All outlets were equipped withpressure valves. Means for heating and cooling the reactor with steamwere also included.

Following the initial charge of aqueous hydrogen chloride, the contentsof the reactor were heated to C. under autogenous pressure. Feeding withapproximately equal weights of hydrogen chloride and tetrahydrofuran wasthen initiated while the temperature was allowed to rise to C. The feedrate of tetrahydrofuran was gradually increased to 5900 pts. by weightper hour. At the same time, liquid over-flow was removed from thereactor, cooled, reduced to about eight pounds pressure and fed to arecovery still. Feed rates and temperatures were controlled so that thereactor pressure did not exceed about 100 p.s.i.g. and the aqueous phaseleaving the reactor contained about 28% hydrogen chloride by weight. Theadjusted hydrogen chloride feed rate was approximately 5910 pts. perhour. Gas equivalent to approximately 3 to 5% of the hydrogen chloridefeed was recycled to a scrubber containing tetrahydrofuran feed.

The process yielded approximately 10,000 pts. per hour of crude,non-aqueous product phase containing 93% 1,4- dichlorobutane, 2%4,4'-dichlorodibutyl ether and 5% unreacted tetrahydrofuran plus a smallamount of hydrogen chloride. This amounts to a net yield of 97%1,4-dichlorobutane with a dichlorobutane to by-product dichlorodibutylether weight ratio of 46.5:1.

The crude two-phase product mixture was fractionally assasso distilled'to remove tetrahydrofuran and hydrogen chlo'- ride for recycling. Theorganic phase wasthendecanted-- lional distillation leaving4,4'-dichlorodibutyl ether as-a still residue.

The net yield of 1,4-dichlorobutane fromrthe recovery process was almostquantitative since, as previously pointedout, distillation of thetwo-phase product'converts tetramethylene chlorhydrin to tetrahydrofuranand hydrogen chloride and hydrolyzes some ofthe dichlorodibutyl ether togive tetramethylene chlorhydrin which is alsouconverted totetrahydrofunan andtlA-dichlorobutane.

No mechanical agitation was-needed'in this prepara tion since sufiicientmixing took place in the feeding process and excess agitation wouldinterfere with eificient decantation of the non-aqueous product phase.

Having described my invention,

I claim:

1. A continuous process for the manufacture of'l,4- dichlorobutanecomprising continuously feeding substantially anhydrous tetrahydrofuranand substantially anhydrous hydrogen chloride in a moleratio of aboutlzZinto the bottom of a liquid mixture comprising a large excess of- 20 to45% by-Weighthydrogen chloride-in water at a temperature in the rangel30 to 150 C. and an autogenous pressure of 50 to 150 p.s.i.g. in-thesubstantial absence of a catalyst,- while continuously decantingreaction product in the form of an non-aqueousupper phase containingl,4-dichlorobutane.as its major constituent and aqueous phase containingapproximate-- 1y one molecular proportion of water per-mole of 1,4-

dichlorobutane in said non-aqueous-phase and notless I than 20% hydrogenchloride by-Weight, sufficient hydrogen chloride being fed to thereactor so as to maintain the hydrogen chloride content of the aqueousphase in the aforesaid range.

2. The process of claim 1 to which is added the steps of fractionallydistilling the two phase product mixture to remove tetrahydrofurandecanting thecnon-aqueous phase from the still residue, neutralizingsaid phase by washing with aqueous alkali to remove hydrogen chlorideand fractionally distilling said neutralized non-aqueous phase toseparate pure 1,4-dichlorobutane.

3. The process of claim 2 inwhich the autogenous pressure is 50 to 100p.s.i.g. and the hydrogen chloride content of the aqueous phase in thereactor is; maintained at to by weight.

4. A continuous'process for the manufacture of 1,4-

dichlorobutane comprising continuously feeding substan tially anhydroustetrahydrofuran and substantiallyranhydrous'hydrogen chloride in a moleratio'of -about--l :2

into th'e bottom of a liquid mixture comprising a large excess of 20'toby weight hydrogen chloride in water at a temperature in the range to170 C. and autogenous pressure in the substantial absence ofacataly st;

while continuouslydecantingreactionproductintheform of-- a non-aqueousphase containing 1,4-dichlorobutaneas its majorv constituentiandanraqueous phase containing. approximately one: molecular: proportion;of water; perv mole of. l,4-dichlorobutane;in;said:=non-aqueous phaseand). not less than 20% hydrogen chloride ,by weight; sutficient :1hydrogen chloride being fed to the reactor soasatomain tain thehydrogenchloride content ofthe aqueous phase in' the aforesaidrrange.

5. Axcontinuous processafonthe manufactureof 1,4- dichlorobutanecomprising continuously feeding, substantially anhydroustetrahydrofuran.andsubstantiallywanrhydrous hydrogen-chlorideina mole,ratio, of about 1 to... 2 into the-.bottom-ofa liquid reaction'mixturecomprising;- a largeexcess-ofan aqueous 25m. 35% by weightsolui tionof'hydrogen. chloride .at a temperature in the. range; to C. andautogeneous pressurerintherange-SO to 150 p.s.i.g.v in the substantialabsence of a catalyst,

While continuously decanting reaction product in the form of anonaqueousruppen phase containing. 1,4-.dichlorobutane as its majorconstituent'and aqueous phase containing approximately one molecularproportion of water per mole of 1,4-dichlorobutane in said non-aqueousphase and 25 to 35% hydrogen chloride by weight, sufficient hydrogenchloride being fed into the aforesaid reaction mixture to maintain thehydrogen. chloride content ofthe aqueous phase in the aforesaid=range of25 to 35%j by weight.

6; The process of-cla-im'S -in-which the -molecular-ratio oftetrahydrofuran to hydrogen chloride in the liquid 1'8 action mixture isnot more than 1:5.

References Cited in the file ofthis patent UNITED STATES PATENTS OTHERREFERENCES Ser. No. 344,582, Trieschmann et al. (A.P.C.), lished-June 8,1943.

pub-

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2,889,380 June 2, 1959 Edward E. Hamel It is hereby certified that errorappears in the-printed specification of the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, Table 1, third column thereof, under the heading Room Temp."third item, for "do" read Top Signed and sealed this 6th day of October1959.

(SEAL) Attest:

KARL I-I, AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner ofPatents

1. A CONTINUOUS PROCESS FOR THE MANUFACTURE OF 1,4DICHLOROBUTANECOMPRISING CONTINUOUSLY FEEDING SUBSTANTIALLY ANHYDROUS TETRAHYDROFURANAN SUBSTANTIALLY ANHYDROUS HLYDROGEN CHLORIDE IN A MOLE RATIO OF ABOUT1:2 INTO THE BOTTOM OF A LIQUID MIXTURE COMPRISING A LARGE EXCESS OF 2/TO 45% BY WEIGHT HYDROGEN CHLORIDE IN WATER AT A TEMPERATURE IN THERANGE 150* TO 150* C. AND AN AUTOGENOUS PRESSUR OF 50 TO 150 P.S.I.G. INTHE SUBSTANTIAL ABSENCSE OF A CATALYST, WHILE CONTINUOUSLY DECANTINGREACTION PRODUCT IN THE FORM OF AN NON-AQUEOUS UPPER PHASE CONTAINING1,4-DICHLOROBUTANE AS ITS MAJOR CONSTITUENT AND AQUEOUS PHASE CONTAININGAPPROXIMATELY ONE MOLECULAR PROPORTION OF WATER PER MOLE OF1,4DICHLOROBUTANE IN SAID NON-AQUEOUS PHASE AND NOT LESS THAN 20%HYLDROGEN CHLORIDE BY WEIGHT, SUFFICIENT HYDROGEN CHLORIDE BEING FED TOTHE REACTOR SO AS TO MAINTAIN THE HYDROGEN CHLORIDE CONTENT OF THEAQUEOUS PHASE IN THE AFORESAID RANGE.